How to change size of ActiveX Control to MDIChildWnd in Visual C++ 6 at run time?

I've created an ActiveX control using .NET and don't know how to resize my control when MDIChildWnd is changing its size

CMyControl* m_pMyControl = new CMyControl;

void CMainFrame::OnFileNewCMdiChildWnd() 
{
   CMDIChildWnd* pMDIChildWnd = new CMDIChildWnd;
   VERIFY(pMDIChildWnd->Create(NULL,_T("My MDIChildWnd"), 
                   WS_CHILD | WS_VISIBLE | WS_OVERLAPPEDWINDOW,       
                   rectDefault, this));
}